Process for the production of a sulfur sorbent

ABSTRACT

Particulate sorbent compositions comprising a mixture of zinc oxide, silica, alumina and a substantially reduced valence cobalt are provided for the desulfurization of a feedstream of cracked-gasoline or diesel fuels in a desulfurization zone by a process which comprises the contacting of such feedstreams in a desulfurization zone followed by separation of the resulting low sulfur-containing stream and sulfurized-sorbent and thereafter regenerating and activating the separated sorbent before recycle of same to the desulfurization zone.

FIELD OF THE INVENTION

This invention relates to the removal of sulfur from fluid streams ofcracked-gasolines and diesel fuels. In another aspect this inventionrelates to sorbent compositions suitable for use in the desulfurizationof fluid streams of cracked-gasolines and diesel fuel. A further aspectof this invention relates to a process for the production of sulfursorbents for use in the removal of sulfur bodies from fluid streams ofcracked gasolines and diesel fuels.

BACKGROUND OF THE INVENTION

The need for cleaner burning fuels has resulted in a continuing worldwide effort to reduce sulfur levels in gasoline and diesel fuels. Thereducing of gasoline and diesel sulfur is considered to be a means forimproving air quality because of the negative impact the fuel sulfur hason the performance of automotive catalytic converters. The presence ofoxides of sulfur in automotive engine exhaust inhibits and mayirreversibly poison noble metal catalysts in the converter. Emissionsfrom an inefficient or poisoned converter contain levels ofnon-combusted, non-methane hydrocarbon and oxides of nitrogen and carbonmonoxide. Such emissions are catalyzed by sunlight to form ground levelozone, more commonly referred to as smog.

Most of the sulfur in gasoline comes from the thermally processedgasolines. Thermally processed gasolines such, as for example, thermallycracked gasoline, visbreaker gasoline, coker gasoline and catalyticallycracked gasoline (hereinafter collectively called “cracked-gasoline”)contains in part olefins, aromatics, and sulfur-containing compounds.

Since most gasolines, such as for example automobile gasolines, racinggasolines, aviation gasoline and boat gasolines contain a blend of atleast in part cracked-gasoline, reduction of sulfur in cracked-gasolinewill inherently serve to reduce the sulfur levels in such gasolines.

The public discussion about gasoline sulfur has not centered on whetheror not sulfur levels should be reduced. A consensus has emerged thatlower sulfur gasoline reduces automotive emissions and improves airquality. Thus the real debate has focused on the required level ofreduction, the geographical areas in need of lower sulfur gasoline andthe time frame for implementation.

As the concern over the impact of automotive air pollution continues, itis clear that further efforts to reduce the sulfur levels in automotivefuels will be required. While the current gasoline products containabout 330 part per million with continued efforts by the EnvironmentalProtection Agency to secure reduced levels, it has been estimated thatgasoline will have to have less than 50 part per million of sulfur bythe year 2010. (See Rock, K. L., Putman H. M., Improvements in FCCGasoline Desulfurization via Catalytic Distillation” presented at the1998 National Petroleum Refiners Association Annual Meeting (AM-98-37)).

In view of the ever increasing need to be able to produce a low sulfurcontent automotive fuel, a variety of processes have been proposed forachieving industry compliance with the Federal mandates.

One such process which has been proposed for the removal of sulfur fromgasoline is called hydrodesulfurization. While hydrodesulfurization ofgasoline can remove sulfur-containing compounds, it can result in thesaturation of most, if not all, of the olefins contained in thegasoline. This saturation of olefins greatly affects the octane number(both the research and motor octane number) by lowering it. Theseolefins are saturated due to, in part, the hydrodesulfurizationconditions required to remove thiophenic compounds (such as, forexample, thiophene, benzothiophene, alkyl thiophenes,alkylbenzothiphenes and alkyl dibenzothiophenes), which are some of themost difficult sulfur-containing compounds to removed. Additionally, thehydrodesulfurization conditions required to remove thiophenic compoundscan also saturate aromatics.

In addition to the need for removal of sulfur from cracked-gasolines,there is also presented to the petroleum industry a need to reduce thesulfur content of diesel fuels. In removing sulfur from diesel byhydrodesulfurization, the cetane is improved but there is a large costin hydrogen consumption. This hydrogen is consumed by bothhydrodesulfurization and aromatic hydrogenation reactions.

Thus there is a need for a process wherein desulfurization withouthydrogenation of aromatics is achieved so as to provide a moreeconomical process for the treatment of diesel fuels.

As a result of the lack of success in providing successful andeconomically feasible process for the reduction of sulfur levels in bothcracked-gasolines and diesel fuels, it is apparent that there is stillneeded a better process for the desulfurization of bothcracked-gasolines and diesel fuels which has minimal affect of octanewhile achieving high levels of sulfur removal.

It is thus an object of the present invention to provide a novel sorbentsystem for the removal of sulfur from fluid streams of cracked-gasolinesand diesel fuels.

Another object of this invention is to provide a process for theproduction of novel sorbents which are useful in the desulfurization ofsuch fluid streams.

Another object of this invention is to provide a process for the removalof sulfur-containing compounds from cracked-gasolines and diesel fuelswhich minimize saturation of olefins and aromatics therein.

A still further object of this invention is to provide a desulfurizedcracked-gasoline that contains less than about 100 parts per million ofsulfur based on the weight of the desulfurized cracked-gasoline andwhich contains essentially the same amount of olefins and aromatics aswere in the cracked-gasoline from which it is made.

Other aspects, objects and the several advantages of this invention willbe apparent from the following description of the invention and theappended claims.

SUMMARY OF THE INVENTION

The present invention is based upon our discovery that through theutilization of cobalt in a substantially reduced valence state,preferably zero, in a sorbent composition there is achieved a novelsorbent composition which permits the ready removal of sulfur fromstreams of cracked-gasolines or diesel fuels with a minimal effect onthe octane rating of the treated stream.

Accordingly, in one aspect of the present invention there is provided anovel sorbent suitable for the desulfurization of cracked-gasolines ordiesel fuels which is comprised of zinc oxide, silica, alumina andcobalt wherein the valence of the cobalt is substantially reduced andsuch reduced valence cobalt is present in an amount to permit theremoval of sulfur from cracked-gasolines or diesel fuels.

In accordance with another aspect of the present invention, there isprovided a process for the preparation of a novel sorbent compositionwhich comprises admixing zinc oxide, silica and alumina so as to form awet mix, dough, paste or slurry thereof, particulating the wet mix,dough, paste or slurry thereof so as to form a particulate granule,extrudate, tablet, sphere, pellet or microsphere thereof; drying theresulting particulate; calcining the dried particulate; impregnating theresulting solid particulate with a cobalt or a cobalt-containingcompound; drying the resulting impregnated solid particulatecomposition, calcining the dried particulate composition and reducingthe calcined product with a suitable reducing agent, such as hydrogen,so as to produce a sorbent composition having a substantial zero valencecobalt content in an amount which is sufficient to permit the removalwith same of sulfur from a cracked-gasoline or diesel fuel stream.

In accordance with a further aspect of the present invention, there isprovided a process for the desulfurization of a cracked-gasoline ordiesel fuel stream which comprises desulfurizing in a desulfurizationzone a cracked-gasoline or diesel fuel with a solid-reduced cobaltmetal-containing sorbent, separating the desulfurized cracked-gasolineor diesel fuel from the sulfurized sorbent, regenerating at least aportion of the sulfurized-solid-reduced cobalt metal metal-containingsorbent to produce a regenerated desulfurized solid cobalt metalmetal-containing sorbent; activating at least a portion of theregenerated desulfurized solid cobalt metal-containing sorbent toproduce a solid reduced cobalt metal metal-containing sorbent; andthereafter returning at least a portion of the resulting reduced cobaltmetal-containing sorbent to the desulfurization zone.

DETAILED DESCRIPTION OF THE INVENTION

The term “gasoline” as employed herein is intended to mean a mixture ofhydrocarbons boiling from about 100° F. to approximately 400° F. or anyfraction thereof. Such hydrocarbons will include, for example,hydrocarbon streams in refineries such as naphtha, straight-run naphtha,coker naphtha, catalytic gasoline, visbreaker naphtha, alkylate,isomerate or reformate.

The term “cracked-gasoline” as employed herein is intended to meanhydrocarbons boiling from about 100° F. to approximately 400° F. or anyfraction thereof that are products from either thermal or catalyticprocesses that crack larger hydrocarbon molecules into smallermolecules. Examples of thermal processes include coking, thermalcracking and visbreaking. Fluid catalytic cracking and heavy oilcracking are examples of catalytic cracking. In some instances thecracked-gasoline may be fractionated and/or hydrotreated prior todesulfurization when used as a feed in the practice of this invention.

The term “diesel fuel” as employed herein is intended to mean a fluidcomposed of a mixture of hydrocarbons boiling from about 300° F. toapproximately 750° F. or any fraction thereof. Such hydrocarbon streamsinclude light cycle oil, kerosene, jet fuel, straight-run diesel andhydrotreated diesel.

The term “sulfur” as employed herein is intended to mean thoseorganosulfur compounds such as mercaptans or those thiophenic compoundsnormally present in cracked gasolines which include among othersthiophene, benzothiophene, alkyl thiophenes, alkyl benzothiophenes andalkyldibenzothiophenes as well as the heavier molecular weights of samewhich are normally present in a diesel fuel of the types contemplatedfor processing in accordance with the present invention.

The term “gaseous” as employed herein is intended to mean that state inwhich the feed cracked-gasoline or diesel fuel is primarily in a vaporphase.

The term “substantially reduced cobalt valence” as employed herein isintended to mean that a large portion of the valence of the cobaltcomponent of the composition is reduced to a value of less than 3,preferably zero.

The present invention is based upon the discovery of applicants that asubstantially reduced valence cobalt component in a particulatecomposition comprising zinc oxide, silica, alumina and cobalt results ina sorbent which permits the removal of thiophenic sulfur compounds fromfluid streams of cracked-gasolines or diesel fuels without having asignificant adverse affect of the olefin content of such streams, thusavoiding a significant reduction of octane values of the treated stream.Moreover, the use of such novel sorbents results in a significantreduction of the sulfur content of the resulting treated fluid stream.

In a presently preferred embodiment of this invention, the sorbentcomposition has a cobalt content in the range of from about 5 to about50 weight percent.

The zinc oxide used in the preparation of the sorbent composition caneither be in the form of zinc oxide, or in the form of one or more zinccompounds that are convertible to zinc oxide under the conditions ofpreparation described herein. Examples of such zinc compounds include,but are not limited to, zinc sulfide, zinc sulfate, zinc hydroxide, zinccarbonate, zinc acetate, and zinc nitrate. Preferably, the zinc oxide isin the form of powdered zinc oxide.

The silica used in the preparation of the sorbent compositions may beeither in the form of silica or in the form of one or moresilicon-containing compounds. Any suitable type of silica may beemployed in the sorbent compositions of the present invention. Examplesof suitable types of silica include diatomite, silicalite, silicacolloid, flame-hydrolyzed silica, hydrolyzed silica, silica gel andprecipitated silica, with diatomite being presently preferred. Inaddition, silicon compounds that are convertible to silica such assilicic acid, sodium silicate and ammonium silicate can also beemployed. Preferably, the silica is in the form of diatomite.

The starting alumina component of the composition can be any suitablecommercially available alumina material including colloidal aluminasolutions and, generally, those alumina compounds produced by thedehydration of alumina hydrates.

The zinc oxide will generally be present in the sorbent composition inan amount in the range of from about 10 weight percent to about 90weight percent, and preferably in an amount in the range of from about15 to about 60 weight percent when such weight percents are expressed interms of the zinc oxide based upon the total weight of the sorbentcomposition.

The silica will generally be present in the sorbent composition in anamount in the range of from about 5 weight percent to about 85 weightpercent, preferably in an amount in the range of from about 20 weightpercent to about 60 weight percent when the weight percents areexpressed in terms of the silica based upon the total weight of thesorbent composition.

The alumina will generally be present in the sorbent composition in anamount in the range of from about 5.0 weight percent to about 30 weightpercent, preferably from about 5.0 weight percent to about 15 weightpercent when such weight percents are expressed in terms of the weightof the alumina compared with the total weight of the sorbent system.

In the manufacture of the sorbent composition, the primary components ofzinc oxide, silica and alumina are combined together in appropriateproportions by any suitable manner which provides for the intimatemixing of the components to provide a substantially homogeneous mixture.

Any suitable means for mixing the sorbent components can be used toachieve the desired dispersion of the materials. Such means include,among others, tumblers, stationary shells or troughs, Muller mixers,which are of the batch or continuous type, impact mixers and the like.It is presently preferred to use a Muller mixer in the mixing of thesilica, alumina and zinc oxide components.

Once the sorbent components are properly mixed to provide a shapeablemixture, the resulting mixture can be in the form of wet mix, dough,paste or slurry. If the resulting mix is in the form of a wet mix, thewet mix can be densified and thereafter particulated through thegranulation of the densified mix following the drying and calcination ofsame. When the admixture of zinc oxide, silica and alumina results in aform of the mixture which is either in a dough state or paste state, themix can be shaped to form a particulate granule, extrudate, tablet,sphere, pellet or microsphere. Presently preferred are cylindricalexrudates having from {fraction (1/32)} inch to ½ inch diameter and anysuitable length. The resulting particulate is then dried and thencalcined. When the mix is in the form of a slurry, the particulation ofsame is achieved by spray drying the slurry to form micro-spheresthereof having a size of from about 20 to about 500 microns. Suchmicrospheres are then subjected to drying and calcination. Following thedrying and calcination of the particulated mixture, the resultingparticulates can be impregnated with cobalt oxide compound or a cobaltoxide precursor.

Following the impregnation of the particulate compositions with theappropriate cobalt compound, the resulting impregnated particulate isthen subjected to drying and calcination prior to the subjecting of thecalcined particulate to reduction with a reducing agent, preferablyhydrogen.

The elemental cobalt, cobalt oxide or cobalt-containing compound can beadded to the particulated mixture by impregnation of the mixture with asolution, either aqueous or organic, that contains the elemental cobalt,cobalt oxide or cobalt-containing compound. In general, the impregnationwith the cobalt is carried out so as to form a resulting particulatecomposition of zinc oxide, silica, alumina and the cobalt metal, cobaltoxide or cobalt oxide precursor prior to the drying and calcination ofthe resulting impregnated composition.

The impregnation solution is any aqueous solution and amounts of suchsolution which suitably provides for the impregnation of the mixture ofzinc oxide, silica and alumina to give an amount of cobalt oxide in thefinal zinc oxide based composition to provide when reduced a reducedcobalt metal content sufficient to permit the removal of sulfur fromstreams of cracked-gasoline or diesel fuels when so treated with same inaccordance with the process of the present invention.

Once the cobalt, cobalt oxide or cobalt oxide precursor has beenincorporated into the particulate calcined zinc oxide, alumina andsilica mixture, the desired reduced valence cobalt metal sorbent isprepared by drying the resulting composition followed by calcination andthereafter subjecting the resulting calcined composition to reductionwith a suitable reducing agent, preferably hydrogen, so as to produce acomposition having a substantial zero valence cobalt content thereinwith such zero valence cobalt content being present in an amount topermit the removal with same of sulfur from a cracked-gasoline or dieselfuel fluid stream.

The solid reduced cobalt metal sorbent of this invention is acomposition that has the ability to react with and/or chemisorb withorgano-sulfur compounds, such as thiophenic compounds. It is alsopreferable that the sorbent removes diolefins and other gum formingcompounds from the cracked-gasoline.

The solid reduced metal sorbent of this invention is comprised of cobaltthat is in a substantially reduced valence state, preferably a zerovalence state. Presently the reduced metal is cobalt. The amount ofreduced cobalt in the solid cobalt reduced metal sorbents of thisinvention is that amount which will permit the removal of sulfur from acracked-gasoline or diesel fuel fluid stream. Such amounts are generallyin the range of from about 5 to about 50 weight percent of the totalweight of cobalt in the sorbent composition. Presently it is preferredthat the reduced cobalt metal be present in an amount in the range offrom about 15 to about 40 weight percent of the total weight of cobaltin the sorbent composition.

In one presently preferred embodiment of the present invention, thereduced cobalt is present in an amount in the range of from about 15 to30 weight percent and the cobalt component has been substantiallyreduced to zero valence.

In another presently preferred embodiment of this invention, zinc oxideis present in an amount of about 38 weight percent, silica is present inan amount of about 31 weight percent, alumina is present in an amount ofabout 8 weight percent and cobalt is present prior to reduction to zerovalence in an amount of about 33 weight percent cobalt oxide.

From the above, it can be appreciated that the sorbent compositionswhich are useful in the desulfurization process of this invention can beprepared by a process which comprises:

(a) admixing zinc oxide, silica and alumina so as to form a mix of samein the form of one of a wet mix, dough, paste or slurry;

(b) particulating the resulting mix to form particulates thereof in theform of one of granules, extrudates, tablets, pellets, spheres ormicrospheres;

(c) drying the resulting particulate;

(d) calcining the dried particulate;

(e) impregnating the resulting calcined particulate with cobalt, cobaltoxide or a precursor for cobalt;

(f) drying the impregnated particulate;

(g) calcining the resulting dried particulate; and

(h) reducing the calcined particulate product of (g) with a suitablereducing agent so as to produce a particulate composition having asubstantial reduced valence cobalt content therein and wherein thereduced valence cobalt content is present in an amount sufficient topermit the removal with same of sulfur from a cracked-gasoline or dieselfuel fluid stream when contacted with the resulting substantiallyreduced valence cobalt particulated sorbent.

The process to use the novel sorbents to desulfurize cracked-gasoline ordiesel fuels to provide a desulfurized cracked-gasoline or diesel fuelcomprises:

(a) desulfurizing in a desulfurization zone a cracked-gasoline or dieselfuel with a solid reduced cobalt metal-containing sorbent;

(b) separating the desulfurized cracked-gasoline or desulfurized dieselfuel from the resulting sulfurized solid reduced cobalt-containingsorbent;

(c ) regenerating at least a portion of the sulfurized solid reducedcobalt-containing sorbent to produce a regenerated desulfurized solidcobalt-containing sorbent;

(d) reducing at least a portion of the regenerated desulfurized solidcobalt-containing sorbent to produce a solid reduced cobalt-containingsorbent thereafter and;

(e) returning at least a portion of the regenerated solid reducedcobalt-containing sorbent to the desulfurization zone.

The desulfurization step (a) of the present invention is carried outunder a set of conditions that includes total pressure, temperature,weight hourly space velocity and hydrogen flow. These conditions aresuch that the solid reduced cobalt-containing sorbent can desulfurizethe cracked-gasoline or diesel fuel to produce a desulfurizedcracked-gasoline or desulfurized diesel fuel and a sulfurized sorbent.

In carrying out the desulfurization step of the process of the presentinvention, it is preferred that the feed cracked-gasoline or diesel fuelbe in a vapor phase. However, in the practice of the invention it is notessential, albeit preferred, that the feed be totally in a vapor orgaseous state.

The total pressure can be in the range of about 15 psia to about 1500psia. However, it is presently preferred that the total pressure be in arange of from about 50 psia to about 500 psia.

In general, the temperature should be sufficient to keep thecracked-gasoline or diesel fuel essentially in a vapor phase. While suchtemperatures can be in the range of from about 100° F. to about 1000°F., it is presently preferred that the temperature be in the range offrom about 400° F. to about 800° F. when treating as cracked-gasolineand in the range of from about 500° F. to about 900° F. when the feed isa diesel fuel.

Weight hourly space velocity (WHSV) is defined as the pounds ofhydrocarbon feed per pound of sorbent in the desulfurization zone perhour. In the practice of the present invention, such WHSV should be inthe range of from about 0.5 to about 50, preferably about 1 to about 20hr⁻¹.

In carrying out the desulfurization step, it is presently preferred thatan agent be employed which interferes with any possible chemisorbing orreacting of the olefinic and aromatic compounds in the fluids which arebeing treated with the solid reduced cobalt-containing sorbent. Such anagent is presently preferred to be hydrogen.

Hydrogen flow in the desulfurization zone is generally such that themole ratio of hydrogen to hydrocarbon feed is the range of about 0.1 toabout 10, and preferably in the range of about 0.2 to about 3.0.

The desulfurization zone can be any zone wherein desulfurization of thefeed cracked-gasoline or diesel fuel can take place. Examples ofsuitable zones are fixed bed reactors, moving bed reactors, fluidizedbed reactors and transport reactors. Presently, a fluidized bed reactoror a fixed bed reactor is preferred.

If desired, during the desulfurization of the vaporized fluids, diluentssuch as methane, carbon dioxide, flue gas, and nitrogen can be used.Thus it is not essential to the practice of the process of the presentinvention that a high purity hydrogen be employed in achieving thedesired desulfurization of the cracked-gasoline or diesel fuel.

It is presently preferred when utilizing a fluidized system that a solidreduced cobalt sorbent be used that has a particle size in the range ofabout 20 to about 1000 micrometers. Preferably, such sorbents shouldhave a particle size of from about 40 to about 500 micrometers. When afixed bed system is employed for the practice of the desulfurizationprocess of this invention, the sorbent should be such as to have aparticle size in the range of about {fraction (1/32)} inch to about ½inch diameter.

It is further presently preferred to use solid reduced cobalt sorbentsthat have a surface area of from about 1 square meter per gram to about1000 square meters per gram of solid sorbent.

The separation of the gaseous or vaporized desulfurized fluids andsulfurized sorbent can be accomplished by any means known in the artthat can separate a solid from a gas. Examples of such means arecyclonic devices, settling chambers or other impingement devices forseparating solids and gases. The desulfurized gaseous cracked-gasolineor desulfurized diesel fuel can then be recovered and preferablyliquefied.

The gaseous cracked-gasoline or gaseous diesel fuel is a compositionthat contains in part, olefins, aromatics and sulfur-containingcompounds as well as paraffins and naphthenes.

The amount of olefins in gaseous cracked-gasoline is generally in therange of from about 10 to 35 weight percent based on the weight of thegaseous cracked-gasoline. For diesel fuel there is essentially no olefincontent.

The amount of aromatics in gaseous cracked-gasoline is generally in therange of about 20 to about 40 weight percent based on the weight of thegaseous cracked gasoline. The amount of aromatics in gaseous diesel fuelis generally in the range of about 10 to about 90 weight percent.

The amount of sulfur in cracked-gasolines or diesel fuels can range fromabout 100 parts per million sulfur by weight of the gaseouscracked-gasoline to about 10,000 parts per million sulfur by weight ofthe gaseous cracked-gasoline and from about 100 parts per million toabout 50,000 parts per million for diesel fuel prior to the treatment ofsuch fluids with the sorbent system of the present invention.

The amount of sulfur in cracked-gasolines or in diesel fuels followingtreatment of same in accordance with the desulfurization process of thisinvention is less than 100 parts per million.

In carrying out the process of this invention, if desired, a stripperunit can be inserted before the regenerator for regeneration of thesulfurized sorbent which will serve to remove a portion, preferably all,of any hydrocarbons from the sulfurized sorbent or before the hydrogenreduction zone so as to remove oxygen and sulfur dioxide from the systemprior to introduction of the regenerated sorbent into the sorbentactivation zone. The stripping comprises a set of conditions thatincludes total pressure, temperature and stripping agent partialpressure.

Preferably the total pressure in a stripper, when employed, is in arange of from about 25 psia to about 500 psia.

The temperature for such strippers can be in the range of from about100° F. to about 1000° F.

The stripping agent is a composition that helps to remove hydrocarbonsfrom the sulfurized solid sorbent. Presently, the preferred strippingagent is nitrogen.

The sorbent regeneration zone employs a set of conditions such that atleast a portion of the sulfurized sorbent is desulfurized.

The total pressure in the regeneration zone is generally in the range offrom about 10 to about 1500 psia. Presently preferred is a totalpressure in the range of from about 25 psia to about 500 psia.

The sulfur removing agent partial pressure is generally in the range offrom about 1 percent to about 25 percent of the total pressure.

The sulfur removing agent is a composition that helps to generategaseous sulfur oxygen-containing compounds such a sulfur dioxide, aswell as to burn off any remaining hydrocarbon deposits that might bepresent. Currently, oxygen-containing gases such as air are thepreferred sulfur removing agent.

The temperature in the regeneration zone is generally from about 100° F.to about 1500° F. with a temperature in the range of about 800° F. toabout 1200° F. being presently preferred.

The regeneration zone can be any vessel wherein the desulfurizing orregeneration of the sulfurized sorbent can take place.

The desulfurized sorbent is then reduced in an activation zone with areducing agent so that at least a portion of the cobalt content of thesorbent composition is reduced to produce a solid cobalt reduced metalsorbent having an amount of reduced metal therein to permit the removalof sulfur components from a stream of cracked-gasoline or diesel fuel.

In general, when practicing the process of this invention, the reductionof the desulfurized solid cobalt-containing sorbent is carried out at atemperature in the range of about 100° F. to about 1500° F. and apressure in the range of about 15 to 1500 psia. Such reduction iscarried out for a time sufficient to achieve the desired level of cobaltreduction in the sorbent system. Such reduction can generally beachieved in a period of from about 0.01 to about 20 hours.

Following the activation of the regenerated particulate sorbent, atleast a portion of the resulting activated (reduced) sorbent can bereturned to the desulfurization unit.

When carrying out the process of the present invention in a fixed bedsystem, the steps of desulfurization, regeneration, stripping, andactivation are accomplished in a single zone or vessel.

The desulfurized cracked-gasoline resulting from the practice of thepresent invention can be used in the formulation of gasoline blends toprovide gasoline products suitable for commercial consumption.

The desulfurized diesel fuels resulting from the practice of the presentinvention can likewise be used for commercial consumption where a lowsulfur-containing fuel is desired.

EXAMPLES

The following examples are intended to be illustrative of the presentinvention and to teach one of ordinary skill in the art to make and usethe invention. These examples are not intended to limit the invention inany way.

Example I

A solid reduced cobalt metal sorbent was produced by dry mixing 20.02pounds of diatomite silica and 25.03 zinc oxide in a mix Muller for 15minutres to produce a first mixture. While still mixing, a solutioncontaining 6.38 pounds of Disperal alumina (Condea), 22.5 pounds ofdeionized water and 316 grams of glacial acetic acid were added to themix Muller to produce a second mixture. After adding these components,mixing continued for an additional 30 minutes. This second mixture wasthen dried at 300° F. for 16 hours and then calcined at 1175° F. for onehour to form a third mixture. This third mixture was then particularizedby granulation using a Stokes Pennwalt granulator fitted with a 50 meshscreen. 200 grams of the resulting granulated mix was then impregnatedwith 148 grams of cobalt nitrate hexahydrate dissolved in 43 grams ofhot (200° F.) deionized water to produce a particulate impregnated mix.The impregnated particulate was dried at 300° F. for one hour and thencalcined at 1175° F. for one hour. 100 grams of the calcined particulatewas impregnated with a solution of 74 grams of cobalt nitratehexahydrate dissolved in 8 grams of hot deionized water to produce animpregnated particulate product which was then dried at 300° F. for onehour and then calcined at 1175° F. for one hour to form a solid cobaltoxide sorbent.

The solid cobalt oxide sorbent was then reduced by subjecting it to atemperature of 700° F., a total pressure of 15 psia and a hydrogenpartial pressure of 15 psi for 30 minutes to produce a solid reducedcobalt sorbent wherein the cobalt component of the sorbent compositionwas substantially reduced to a zero valence state.

Example II

The solid reduced cobalt sorbent as prepared in Example I was tested forits desulfurization ability as follows.

A one inch quartz reactor tube was loaded with the indicated amounts ofthe sorbent of Example I. This solid reduced cobalt sorbent was placedon a frit in the middle of the reactor. Gaseous cracked-gasoline havingabout 345 parts per million sulfur by weight of the sulfur-containingcompounds based on the weight of the gaseous cracked-gasoline and havingabout 95 weight percent thiophenic compounds (such as for example, alkylbenzothiphenes, alkyl thiophenes, benzothiophene and thiophene) based onthe weight of sulfur-containing compounds in the gaseouscracked-gasoline was pumped upwardly through the reactor. The rate was13.4 milliliters per hour. This produced sulfurized solid sorbent anddesulfurized gaseous cracked-gasoline.

In Run 1, hydrogen was added to the gasoline feed at a partial pressureof 6.6 psi (out of a total pressure of 15 psi) resulting in a reductionin gasoline sulfur to 15-25 parts per million.

After Run 1, the sulfurized sorbent was subjected to regenerationconditions that included a temperature of 900° F., a total pressure of15 psia and an oxygen partial pressure of 0.6 to 3.1 psi for a period of1-2 hours. Such conditions are hereinafter referred to as “regenerationconditions” to produce a desulfurized cobalt-containing sorbent. Thissorbent was then subjected to reducing conditions that included atemperature of 700° F., a total pressure of 15 psia and a hydrogenpartial pressure of 15 psi for a time period of 0.5 hours. Suchconditions are hereinafter referred to as “reducing conditions”.

In the next series of runs (2-6), after each run the sulfurized sorbentwas subjected to regeneration and reducing conditions as describedabove.

Runs 2 and 3 were essentially repeats of Run 1 indicating that thesorbent can be regenerated to a fresh state where it can reduce thesulfur content of cracked-gasoline to about 5 parts per million.

A composite of product gasoline from each of the Runs 1 and 2 wassubjected to a test to determine its research octane number (RON), usinga method as described in ASTM 2699 procedure entitled “Research OctaneNumber of Sparked Ignition Engine Fuel”. The RON for the products fromRuns 1 and 2 was 91.4 as compared to the RON of 91.1 for thecracked-gasoline feed, indicating that the octane of thecracked-gasoline was not affected by carrying out the inventivedesulfurization process.

In Runs 4-7, the effect of hydrogen partial pressure was studied. As thehydrogen partial pressure is reduced (Run 4), the ability of the sorbentto desulfurize cracked-gasoline diminished. When no hdyrogen is used inthe process (Run 5), very little reduction in the sulfur content iseffected. When the hydrogen partial pressure was increased to 13.2, thesorbent essentially reduced the cracked-gasoline to less than 5 partsper million.

Run 7 was a repeat of Runs 1-3 and indicates that even after repeatedcycles of desulfurization, regeneration and reduction or activation, theability of the sorbent to remove sulfur from cracked gasoline did notdiminish, for example compare Run 1 to Run 7.

The results of this series of runs is set forth in Table 1.

TABLE 1 Reactor Run Number Conditions 1 2 3 4 5 6 7 Amount 10 10 10 1010 10 10 (grams) TP¹ 15 15 15 15 15 15 15 HPP² 6.6 6.6 6.6 2.25 0 13.26.6 ° F. 700 700 700 700 700 700 700 TOS³ Sulfur⁴ 1 15 5 5 75 285 5 15 220 5 <5 105 385 <5 15 3 25 5 <5 110 320 <5 10 4 25 5 115 <5 5 5 24 10 <510 RON 91.4 91.4 ¹Total pressure in psia. ²Hydrogen particle pressure inpsia. ³The time on stream in hours. ⁴The amount of sulfur-containingcompounds left in the desulfurized cracked-gasoline in parts per millionsulfur by weight based on the weight of the desulfurizedcracked-gasoline.

The specific examples herein disclosed are to be considered as beingprimarily illustrative. Various changes beyond those described will nodoubt occur to those skilled in the art; and such changes are to beunderstood as forming a part of this invention insofar as they fallwithin the spirit and scope of the appended claims.

That which is claimed is:
 1. A process for the production of a sorbentcomposition suitable for the removal of sulfur from a cracked-gasolineor diesel fuel stream which comprises: (a) admixing of zinc oxide,silica and alumina so as to form a mix thereof; (b) particulating theresulting mix so as to form particles thereof; (c) drying theparticulate of step (b); (d) calcining the dried particulate of step(c); (e) impregnating the resulting calcined particulate of step (d)with cobalt or a cobalt-containing compound; (f) drying the impregnatedparticulate of step (e); (g) calcining the dried particulate of step(f); and thereafter (h) reducing the resulting calcined particulate ofstep (g) with a suitable reducing agent under suitable conditions toproduce a particulate composition wherein the valence of essentially allof the cobalt therein is zero such that the reduced cobalt-containingcomposition will affect the removal of sulfur from a stream ofcracked-gasoline or diesel fuel when said stream is contacted with saidreduced cobalt-containing composition.
 2. A process in accordance withclaim 1 wherein said mix is in the form of one of a wet mix, dough,paste or slurry.
 3. A process in accordance with claim 1 wherein saidparticles are in the form of one of granules, extrudates, tablets,spheres, pellets or microspheres.
 4. A process in accordance with claim1 wherein said zinc oxide is present in an amount in the range of fromabout 10 to about 90 weight percent, said silica is present in an amountin the range of about 5 to about 85 weight percent and said alumina ispresent in an amount in the range of from 5 about 5 to about 30 weightpercent.
 5. A process in accordance with claim 4 wherein saidparticulate is impregnated with cobalt or a cobalt compound in an amountto provide a cobalt content therein in an amount in the range of fromabout 5 to about 50 weight percent.
 6. A process in accordance withclaim 1 wherein said particulate is dried in steps (c) and (f) at atemperature in the range of about 150° F. to about 350° F.
 7. A processin accordance with claim 1 wherein said dried particulate is calcined insteps (d) and (g) at a temperature in the range of about 400° F. toabout 1500° F.
 8. A process in accordance with claim 2 wherein said zincoxide is present in an amount in the range of about 45 to 60 weightpercent, said silica is present in an amount in the range of about 15 to60 weight percent, said alumina is present in an amount in the range ofabout 5.0 to about 15 weight percent and said cobalt is present in anamount in the range of about 15 to about 40 weight percent.
 9. A processin accordance with claim 1 wherein said calcined, impregnatedparticulated mix is reduced in a reduction zone with a reducing agentunder suitable conditions to effect a substantial reduction of thevalence of the cobalt content so as to provide an amount of reducedvalence cobalt metal such that the resulting composition will effect theremoval of sulfur from a cracked-gasoline or diesel fuel when treatedwith same under desulfurization conditions.
 10. A process in accordancewith claim 9 wherein said reduced valence cobalt is present in an amountin the range of about 5 to about 40 weight percent, based on the totalweight of the sorbent composition.
 11. A process in accordance withclaim 9 wherein the reduction of cobalt is carried out at a temperaturein the range of about 100° F. to about 1500° F. and at a pressure in therange of about 15 to about 1500 psia for a time sufficient to permit theformation of the desired reduced valence cobalt component.